Marshall jmp/jcm questions

[mchn13]

Ive got a 2203, and a jmp 50watt, my other guitarist has a 2204. Both mine have el34's, his 50 watter has kt88's. Now my 2203 is the loudest/fullest of the three, but only by a tiny fraction. His actually has a little more low end. Im trying to get my jmp to s
Be as loud/ full sounding as his. Mine might need a bias, gonna get it checked tomorrow, but have been thinking about going to kt77's. Think that might give it that little bit more??
Any mods to switch over to kt77's or just a re bias?

 

[mchn13]

For reference, at practice my jmp was at 4 on the master, his jcm was at 2. My amp has been gone through recently. New caps etc...., could the difference in volume fullness just be the 88's?

 

[gtrwun]

If you like his tone, I'd get it modded for 88's. Simple enough to do. Im not a fan of 77's but thats a personal thing.

 

[stephen sawall]

Even if you have two identical amps they all sound different.

I am pretty sure all you need to do with the KT77 is bias....but KT77 do not sound anything like KT88. Preamp tube V1 in your amp will have the biggest effect on tone & gain.

100 watt amps are not much louder than 50 watt amps in my experience.

 

[Metalone72]

KT88's Rawk! Haven't really heard any KT77's in action.

 

[mchn13]

What would have to be modded in an el34 modEl to use kt 88's?

 

[stephen sawall]

I think it is the same mod as changing EL34 to 6550 ?

This requires working over live circuits with 400+ volts. It ain't worth frying to save a couple $$. It is a common conversion and easy to get done.
In my experience changing around the first preamp tube effects the sound more than changing the power tubes.
But will admit 3 of the 5 amps I use the most have KT88 in them right now.

 

[gtrwun]

Regarding the swap to KT88's........give this a glance.

EL34 amplifiers are a little trickier. I know a lot of people that believe you can just swap out EL34's with KT88's and re-bias. While I've seen people do this with no problems, I don't recommend it. Most EL34 based amplifiers are going to require a change of the bias feed resistors from 220k to 100k. The KT88 (and 6550 for that matter) can't quite deal with the higher grid resistance from the 220k resistor (these are typically the rating found in EL34 circuits). Not changing it will both shorten the life of the tube (probably dramatically) and also not allow the KT88 to be run close to their design ratings. In other words, if you don't change these resistors out, the KT88 will not perform well and may not sound good at all. As with any other tube swap, make sure the rest of the circuit is designed to accommodate them. Your tech or manufacturer would be able to tell you.

 

[Anonymous]

Depending on your amps....You may only have to remove a piggy backed resistor to get it to run KT88/6550 tubes...They most likely came stock with them.
Post a gut shot of your amps. If they are both JMP's...there's a 99.99.99% chance they did

 

[mchn13]

Cool ill get a pick of the guts tomorrow. I didnt mean to say I was going to do the mod to run kt88's. But would like to be informed as to wht i would need to talk to the tech about getting it done. Im completely dumb about how to make an amp work lol. I just know my jmp is nt as loud or as full as my buddys jcm800, and would like to get it in the same ballpark.

 

[mchn13]

And, if i can get it there with el34's.. Even better. My 2203 with el34's just crushes, and is one of the loudest punchiest things ive ever heard.

 

[LP Freak]

It could just be the amp. Some amps just don't have it.

 

[Rogue]

It could just be the amp. Some amps just don't have it.

That's what I'm thinking. You can do a whole lot of trying this and that, spending a bunch of cash and never getting it there.

Retube it with some good tubes, preamp and power. Rebias and see where it's at.

 

[Rash]

That's what I'm thinking. You can do a whole lot of trying this and that, spending a bunch of cash and never getting it there.

Retube it with some good tubes, preamp and power. Rebias and see where it's at.

Exactly my experience, especially with old marshalls...try winged =C= sed Power tubes and old! Blackburn Mullard or old 60!!!ties Siemens in the first preamp stage, my favourite marshall tubes.

BTW an old marshall is not a chunk/bass monster, slight differences are not that important, let the bass player do that job => induces better music with better bass lines , the complexity/woodyness/directness midrange is what make these marshalls shine, nothing! compares to it, tried a quite cool bogner Goldfinger (very flexible) quite cool clean sound) with el34 and 6v6 next to my old jmp last month.....the bogner was not in the same class.

Kai

 

[mchn13]

That's what I'm thinking. You can do a whole lot of trying this and that, spending a bunch of cash and never getting it there.

Retube it with some good tubes, preamp and power. Rebias and see where it's at.

Exactly my experience, especially with old marshalls...try winged =C= sed Power tubes and old! Blackburn Mullard or old 60!!!ties Siemens in the first preamp stage, my favourite marshall tubes.

BTW an old marshall is not a chunk/bass monster, slight differences are not that important, let the bass player do that job => induces better music with better bass lines , the complexity/woodyness/directness midrange is what make these marshalls shine, nothing! compares to it, tried a quite cool bogner Goldfinger (very flexible) quite cool clean sound) with el34 and 6v6 next to my old jmp last month.....the bogner was not in the same class.

Kai

I hear ya, but im not talking about bass here. I dont use excessive bass or low tunings. To simplify, just asking opinions on whether, 88's would make a difference in volume or fullness( not bass ). Im taking it to a tech today for a bias on a new set of tad el34b's i have.
It might just be out of whack. Not trying to be snarky, but im not a kid trying to get a marshall to sound like a death machine.

 

[Rogue]

Just to make sure, were you running all the amps through the same cab?

 

[mchn13]

Just to make sure, were you running all the amps through the same cab?

Yup. All three through two identical cabs. Me and my other guitarist have the same cab setup, and we were playing our set at practice. On my 100 watt i have my bass at half and my volume at 2. Thats the thing, i was only just keeping up with him, and i had the jmp bolume at 4-5.

 

[Rash]

Had the TAD only short time in my Amp, was also ok!

Yes, cab and speaker makes a bigger difference....

V30 have not that much bass

With Marshall compare Scumback M75 (kills all new Greenbacks), V30, 75.....they differ a lot....

I do not like other valves than el34 in Marshalls, effects the midrange in a bad way.....

Kai

 

[Shiny_Surface]

I hear ya, but im not talking about bass here. I dont use excessive bass or low tunings. To simplify, just asking opinions on whether, 88's would make a difference in volume or fullness( not bass ). Im taking it to a tech today for a bias on a new set of tad el34b's i have.
It might just be out of whack. Not trying to be snarky, but im not a kid trying to get a marshall to sound like a death machine.

I could be completely wrong but I read that Marshall may have raised the plate voltage on the early JCM 800 even though the MV JMP and early 800s have the same basic circuit/topology.

Higher plate voltage makes for a bolder sound I think.

 

[Schaf]

For reference, at practice my jmp was at 4 on the master, his jcm was at 2. My amp has been gone through recently. New caps etc...., could the difference in volume fullness just be the 88's?

Are there any mods to the amp and where are you running the preamp gain? Cause if you're running the master at 4, that thing should be ripping your face off. I don't know where you would be able to gig that loud or even hear a drummer for that matter. I have a 2204 w el34's and i can't run the master at even 2 and it's freakin ripping at that setting.

BTW, I have one 2204 with el34's and one with 6550's and the difference isn't as dramatic as one would think. I personally prefer the el34's. But that's just me. Actually you can dial the amps in to sound almost identical.